1. Field of the Invention
The invention relates to an electric or electronic sheet control device for sheet-transferring cylinders of printing machines, including detecting elements disposed on the cylinder in the area of a cylinder edge cooperating with the grippers, for detecting a leading edge of a sheet.
Such a sheet control device is known from German Petty Patent DE-GM 77 00 430. In that sheet control device, two detecting elements are disposed at a certain distance from each other in the area of the cylinder edge cooperating with the grippers, thus registering whether or not a sheet has been gripped and recognizing a misaligned sheet.
2. Description of the Related Art Including Information Disclosure Under 37 C.F.R. 1.97-1.99
However, the leading edge of the sheet may be curved when being taken by the grippers, as a result of an irregular sheet transport. In such a case, the leading edge of the sheet has a concave or convex shape because the lateral parts of the sheet are conveyed faster than the middle part thereof, or vice versa. The known sheet control device does not permit the detection of such a fault.